Cartridge fuse holder and indicator



July 31, 1962 E. BORYS 3,047,695

CARTRIDGE FUSE HOLDER AND INDICATOR Filed Nov. 13, 1959 Unite W8 PmmiQ 3,047,695 CARTRIDGE FUSE HOLDER AND INDICATOR Emil Borys, 710 Old Rand Road, Lake Zurich, Ill. Filed Nov. 13, 1959, Ser. No. 852,914 4 Claims. (Cl. 200121) electrical connections thereto on the interior of the device,

one can readily tell when the fuse has blown because the neon bulb will be illuminated in that condition but not when the fuse is unblown.

The cartridge-type fuse may be readily removed when blown or when it is desired to replace it with a different type of. fuse. Thus, the fuse holder and indicator of the present invention is a permanent item, the life of'which is only dependent on the life of the neon bulb which is good for-many thousands of hours of operation. Since the neon bulb'glows orisfin'operation only when the fuse is blown, it will be seen that the device has indefinite life for practical purposes.

Theobject of my invention is the provision of a screw plug type cartridge fuse holder and adaptor of the class described which is foolproof, versatile in use, and formed of mass produced, low cost components which may be readily assembled.

Other objects of the invention will, in part, be obvious, and will in part appear hereinafter.

For a more complete understanding of the nature and scope of my invention, reference may now be had to the following detailed description thereof, taken in connection with the accompanying drawings wherein:

FIG. 1 is a top plan view of a screw plug type cartridgetype fuse holder and indicator forming one embodiment of my invention;

FIG. 2 is a sectional view taken on line 22 of FIG. 1 with certain parts being shown in elevation; and

FIG. 3 is a circuit diagram by means of which the operation of the device may be described and illustrated.

Referring to FIGS. 1 and. 2, the screw plug type cartridge fuse holder and indicator is designated generally at 1. It comprises a hollow cylindrical plug body 2 having a rear end wall portion 3 and a cylindrical shell or outer wall portion 4. On the interior of the body 2 there is an integrally formed baffle 5 which projects from. the inside of the end wall 3 as a base and constitutes a center well for centering and housing the inner portion of a cartridge type fuse 6.

A screw shell 7 formed of copper, brass or other electrically conducting material is press fitted over the front end of the body 2 with its inturned flange 8 serving to secure a centrally apertured washer 9 in place over the front end of the fuse body 2. The washer 9 serves to support a small diameter screw shell 10 formed of copper, brass or like material which serves as a female support for a set screw contact member 11 which is cross slotted in known manner.

A spring detent type of terminal 12 is disposed in the bottom (or upper end as shown in FIG. 2) of the well 5 so as to be in co-axial alignment with the set screw contact 11. It will thus be seen that the cartridge fuse 6 is securely retained within the fuse holder and indicator 1 with the opposite terminals thereof :being engaged by the M 3,047,695 Patented J y 1962 set screw contact 11 and the detent terminal 12, respecti-vely. By removing the set screw 11, the cartridge 6 may be readily removed and replaced in a matter of a few seconds.

A conductor 13, which may be formed of the same piece of spring tempered conducting metal as the terminal 12, interconnects the latter with the outer screw shell 7. The conductor 13 projects through a small opening 14 provided therefor in the baflie or well 5 and through another small opening 15 in the cylindrical wall 4. The connection of the terminal 13 to the shell 7 is by means of solder.

A miniature neon bulb 16 is disposed in the annular space between the baffle 5 and the outer Wall 4 with the tip end 17 projecting through a small aperture 18 provided therefor in the end wall 3. These miniature neon bulbs are well known and commercially available in quantity. When a suflicient difference in potential or voltage is impressed across the grids or electrodes, the neon or other gas on the interior of the envelope will be ionized and glow.

One of the outside terminals of the neon bulb 16 is electrically connected to the center screw shell 10 by means of a conductor 19, while the second terminal is connected to the outer screw shell 7 by a conductor 20. The latter conductor projects through a small aperture 21 provided therefor in the side wall 4 of the plug body 2. It may be desirable to place a resistor 22 in series circuit relationship in the conductor 19. These miniature resistors 22 may be obtained commercially in any desired rating such as between 50,000 and 220,000 ohms. If the cartridge fuse holder and indicator 1 is to be used in circuits where the voltage does not exceed 24 volts for example, it will usually be unnecessary to include a resistor 22, but simply use a miniature neon bulb 16 of a type that will have a long life at such voltages. On the other hand, if the cartridge fuse holder and indicator is to be used in circuits where the voltage is say 115 or 220 volts, then it will usually be more economical to insert a miniature resistor 22 of the proper rating in the conductor 19 thereby protecting the neon bulb and obtaining the full life thereof. It will be seen that all of the components of the device 1 may be mass produced at low cost. In fact, such com ponents as the outer screw shell 7, the washer 9, the inner screw shell 10, the neon bulb 16, the resistor 22 and the cartridge fuses 6 are standard components or items which can be procured on the open market. Therefore, the body 2 is the only special part and this may be readily molded from porcelain or a plastic such as Bakelite.

Referring to FIG. 3, a source of alternating current such as 115 volts is indicated at 25 with a pair of conductors 26 and 27 leading therefrom to a load diagrammatically indicated at 28. The cartridge fuse holder and indicator 2 of FIGS. 1 and 2 is indicated in circuit relationship in conductor 27. That is, the cartridge fuse is indicated at 6 and the neon bulb indicated at 16. As long as the fuse 6 is not blown, it provides a shunt or short across the neon bulb 16 so that no potential is impressed across the grids or electrodes within the gas filled envelope. Hence the bulb does not blow. However, if the fuse 6 blows or fails for any reason, then a potential will be impressed on one of the grids and the gas will be ionized and glow with the ions draining off to ground through the opposite grid or electrode. The glowing of the neon bulb thus tells one that the fuse 6 has blown and requires attention and replacement.

Two typical uses of the cartridge fuse holder and indicator 1 will now be described. In the operation of Teletype machines, it is the practice to have large banks of fuses of the so-called slow blow type. This is a type of fuse that is well known and will withstand impulses or loads for say a half second or more without blowing.

Thus, when a machine comes on and draws a high momentary load until it gets into operation, one of these slow blowing fuses will not fail or blow unless the load stays on for longer than the normal time. Heretofore, whenone fuse blew in a bank containing a large number, it was necessary to call an electrician to trace down which of the large number of fuses was blown. This not only shut the machines down for a time but was expensive from the standpoint of getting the electrician to the site and then his time in finding the faulty fuse and replacing it.

If the conventional slow blow fuse is replaced with one of the cartridge fuse holder and indicator devices 1, when an inner cartridge fuse 6 blows the lamp 16 of that holder and indicator glows and any operator may readily detect the blown fuse and replace it with another of the proper type and then replace the holder and indicator in the socket.

It will be understood that the cartridge type fuses 6 may have any desired rating and may be either of the slow blow type or of the instantaneous type.

A second use of the cartridge fuse holder and indicator 1 is for indicating current in a lamp socket. For example, in an ordinary house circuit where there has been a short, the cartridge fuse 6 may be removed and then the device screwed into the lamp socket. If the glow lamp 16 glOWs then it is an indication that the socket is live.

It will be understood that certain changes of an obvious nature may be made in the embodiment of the invention described above in connection with the accompanying drawings without departing from the spirit and scope of the invention. Accordingly, the foregoing description is not intended to be interpreted as limiting but rather to be interpreted in an illustrative sense.

What I claim as new is:

l. A screw plug type cartridge fuse holder and indicator comprising, a plug body formed of insulation material having an exposed window in the outer end thereof, a screw shell contact with an inturned flange secured over and surrounding the front end of said body, a centrally apertured washer formed of insulation material secured over the front end of said body by said inturned flange, a female support member formed of electrically conductive material disposed in the central aperture of said washer, a male insert formed of electrically conductive material removably insertable in said female support member to serve as a center contact, said plug body having a central well on the interior thereof in alignment with said male insert for receiving a cartridge type fuse therein, a terminal positioned on the inside of said plug body at the bottom of said central well, a first conductor interconnecting said terminal with said screw shell, said plug body having :a second well therein in alignment with said window, a miniature neon type bulb disposed within said second well with the tip end projecting into and viewable through said window, a second conductor interconnecting said female support member with one terminal of said bulb, and a third conductor interconnecting said second terminal of said bulb with said screw shell, said window being large enough to accommodate said tip end but too small to accommodate the main body of said bulb.

2. The screw plug type cartridge fuse holder and indicator of claim 1 wherein a miniature resistor is disposed in series in at least one of said second and third conductors.

3. A screw plug type cartridge fuse holder and indicator comprising a hollow cylindrical plug body formed of insulation material having a central bafile integrally formed on the end wall of said body and forming a center well on the interior of said plug and there being a small aperture in the end wall of said body opening into the annular space between said well and the plug body side wall, a screw shell outer contact secured on and surrounding the front end of said body having an inturned annular flange on the front end thereof, a centrally apertured washer formed of insulation material secured over the front end of said body with the margin thereof locked between the end of said body on one side and said inturned flange on the opposite side, a small screw shell mounted in the central aperture in said washer, a set screw for said small screw shell serving as a center contact, :a terminal positioned in the bottom of said center well whereby a cartridge type fuse is adapted to be secured within said plug body with one end terminal being engaged by said set screw and the other end terminal engaging said well terminal, a first conductor interconnecting said well terminal withsaid outer screw shell, a miniature neon type bulb disposed within said annular space with the end thereof projecting into said small aperture whereby it is exposed to view, a second conductor interconnecting said small screw shell with one terminal of said bulb, and a third conductor interconnecting the second terminal of said bulb with said outer screw shell.

4. The device of claim 3 wherein a miniature resistor is disposed in series in at least one of said second and third conductors.

References Cited in the file of this patent UNITED STATES PATENTS 1,957,345 Kriegstedt May 1, 1934 2,009,089 Lamar July 23, 1935 2,206,782 Linton July 2, 1940 2,422,886 Chittum June 24, 1947 

